Storage Backends¶

Storage scheme¶

limits uses a url style storage scheme notation (similar to the JDBC driver connection string notation) for configuring and initializing storage backends. This notation additionally provides a simple mechanism to both identify and configure the backend implementation based on a single string argument.

The storage scheme follows the format {scheme}://{parameters}

limits.storage.storage_from_string() is provided to lookup and construct an instance of a storage based on the storage scheme. For example:

import limits.storage
uri = "redis://localhost:9999"
options = {}
redis_storage = limits.storage.storage_from_string(uri, **options)

The additional options key-word arguments are passed as is to the constructor of the storage and handled differently by each implementation. Please refer to the class documentation of Backend Implementations for details.

Examples¶

In-Memory¶

The in-memory storage (limits.storage.MemoryStorage) takes no parameters so the only relevant value is memory://

Memcached¶

Requires the location of the memcached server(s). As such the parameters is a comma separated list of {host}:{port} locations such as memcached://localhost:11211 or memcached://localhost:11211,localhost:11212,192.168.1.1:11211 etc… or a path to a unix domain socket such as memcached:///var/tmp/path/to/sock

Depends on: pymemcache

Memcached on Google App Engine¶

Requires that you are working in the GAE SDK and have those API libraries available. :code: gaememcached://

Redis¶

Requires the location of the redis server and optionally the database number. redis://localhost:6379 or redis://localhost:6379/n (for database n).

If the redis server is listening over a unix domain socket you can use redis+unix:///path/to/sock or redis+unix:///path/to/socket?db=n (for database n).

If the database is password protected the password can be provided in the url, for example redis://:foobared@localhost:6379 or redis+unix//:foobered/path/to/socket if using a UDS..

Depends on: redis-py

Redis over SSL¶

Redis does not support SSL natively, but it is recommended to use stunnel to provide SSL suport. The official Redis client redis-py supports redis connections over SSL with the scheme rediss. rediss://localhost:6379/0 just like the normal redis connection, just with the new scheme.

Depends on: redis-py

Redis with Sentinel¶

Requires the location(s) of the redis sentinal instances and the service-name that is monitored by the sentinels. redis+sentinel://localhost:26379/my-redis-service or redis+sentinel://localhost:26379,localhost:26380/my-redis-service.

If the database is password protected the password can be provided in the url, for example redis+sentinel://:sekret@localhost:26379/my-redis-service

Depends on: redis-py

Redis Cluster¶

Requires the location(s) of the redis cluster startup nodes (One is enough). redis+cluster://localhost:7000 or redis+cluster://localhost:7000,localhost:70001

Depends on: redis-py-cluster